The present disclosure herein relates to a color changeable device, and more particularly, to the electrochromic device.
Liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs) have been widely used as information displays. These devices generate various colors by transmitting light from their own light source through a color filter or generate colors from light that is emitted in response to a current flow in a material itself. On behalf of such emissive display devices, interest in reflective displays using external light has been greatly increased.
Electrochromism denotes characteristics in which optical properties, such as color, transmittance, or reflectance, of a material are reversibly changed by an electrochemical reaction when an electric field is applied. With respect to an electrochromic device, its color and transmittance may be changed according to an applied electric field, an external light source is not required, and its reflectance is excellent. Thus, the electrochromic device has been used as an optical shutter, an electrochromic mirror (ECM) for automobiles, a reflective display, or a smart window.
In the electrochromic device, when an ion conductive layer or an electrolyte is disposed between electrodes and an external voltage is applied to the electrodes, a potential difference between the electrodes occurs. Then, ions or electrons in the ion conductive layer or the electrolyte move to an electrochromic layer to cause a redox reaction. Due to the redox reaction of the electrochromic layer, the color or transmittance of the electrochromic device changes. For the color changes of the electrochromic device, diffusion of ions from the electrolyte to the electrochromic layer is required.